#app {
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  min-height: 100vh;
  background-color: #f8f8f8;
}

#board {
  border: 2px solid skyblue;
}

.util {
  display: flex;
  justify-content: space-between;
  background-color: skyblue;
  width: 800px;
  border: 2px solid skyblue;
  padding: 20px ;

}

.util_left {
  display: flex;
}

.util_left .square {
  margin-right: 10px;
}

.square {
  width: 50px;
  height: 50px;
  background-color: #fff;
  cursor: pointer;
  text-align: center;
  line-height: 50px;
  font-size: 20px;
  font-weight: 700;
}

.brush_color{
  border: 5px solid #fff;
}

/* 去掉右侧上下箭头 */
.brush_size::-webkit-outer-spin-button,
.brush_size::-webkit-inner-spin-button {
  -webkit-appearance: none;
}